Cleaning apparatus

ABSTRACT

A cleaning apparatus for cleaning the residual toner image from an electrostatic plate of an electrostatic reproduction apparatus incorporates a continuous wiper member having an outer layer of a compliant material which has a resistivity of less than 10 8 ohm.- centimeters and an outer skin thereon. The wiper member is connected to ground. As the wiper member wipingly engages the toner particles, the toner partricles are mechanically dislodged from the surface of the electrostatic plate. Additionally, an image charge is produced on the outer skin surface of the conductive wiper member equal to but opposite in sign from the charge on the toner particles in proximity therewith. This image charge causes the toner particles to adhere to the skin surface as the wiper member moves away from the electrostatic plate regardless of the sign of the toner charge. A further cleaning member is utilized to remove the toner particles from the skin surface of the wiper member which travels in a closed loop past the electrostatic plate and the further cleaning member.

United States Patent [1 1 Bacon et al.

[ CLEANING APPARATUS [75] Inventors: James L. Bacon; Henry W. Simpson,

both of Lexington, Ky.

22 Filed: Dec. 26, 1972 211 Appl: No.: 317,974

[52] U.S.Cl.

[51] Int. Cl B08b 1/02 [58] Field of Search 15/15; 96/1 A, 1.4;

[56] References Cited UNITED STATES PATENTS 2,752,271 6/1956 Walkup etal. l5/l.5 X 3,438,706 4/1969 Tanaka et al, 1 1 355/15 3,580,673 5/1971Yang 355/15 3,634,077 l/l972 Sullivan 355/15 X 3,655,373 4/1972 Fisheret al. 15/].5 X 3,728,016 4/1973 Harbour et al. 15/1.5 X 3,781,10512/1973 Meagher 96/].4

Primary Examiner-Edward L. Roberts Attorney, Agent, or Firm.lohn W.Girvin, Jr.

[ 1 May 20,1975

[57] ABSTRACT A cleaning apparatus for cleaning the residual toner imagefrom an electrostatic plate of an electrostatic reproduction apparatusincorporates a continuous wiper member having an outer layer of acompliant material which has a resistivity of less than 10*" ohm.-centimeters and an outer skin thereon. The wiper member is connected toground. As the wiper member wipingly engages the toner particles, thetoner partricles are mechanically dislodged from the surface of theelectrostatic plate. Additionally, an image charge is produced on theouter skin surface of the conductive wiper member equal to but oppositein sign from the charge on the toner particles in proximity therewith.This image charge causes the toner particles to adhere to the skinsurface as the wiper member moves away from the electrostatic plateregardless of the sign of the toner charge. A further cleaning member isutilized to remove the toner particles from the skin surface of thewiper member which travels in a closed loop past the electrostatic plateand the further cleaning member.

5 Claims, 4 Drawing Figures HAYZOIQYB FIG. 1

CLEANING APPARATUS CROSS-REFERENCES TO RELATED APPLICATIONS Thefollowing applications are assigned to the same assignee as the presentapplication:

BRIEF BACKGROUND OF INVENTION 1. Field This invention relates to thecleaning of toned electrostatic images on a plate and, moreparticularly, to an improved compliant wiper cleaning apparatus.

2. Description of 'the'Prior Art In well-known electrostatic printingprocesses, an electrostatic plate bearing a latent electrostatic imageis developed by applying a developer material including chargedelectroscopic toner particles to the plate. The charged toner isselectively attracted to the image areas on the plate and iselectrostatically maintained thereon. The toned image is thereaftertransferred to a support surface such as paper and thereafterpermanently affixed to the support surface. Transfer of the tonerparticles from the image area on the plate to the support surface isoften effected by a corona generating device which imparts anelectrostatic charge to attract the toner particles from the plate tothe support surface. Other transfer techniques such as pressure transferand heat transfer are also utilized. In any event, a residual tonerimage usually remains on the plate after transfer which must be cleanedtherefrom before the plate may be reused for subsequent imaging.

Well-known brush and web-type cleaning apparatus have often beenemployed to remove the residual toned image from the electrostatic platein prior electrostatic printing apparatus. The brush-type cleaningdevices usually comprise one or more rotating brushes which brush thetoner powder from the plate into a stream of air which is exhaustedthrough a filtering system. Often, a knockoff bar or similar apparatusis utilized in conjunction with the rotating brush to free' the tonerparticles from the brush thus maintaining the brush operable over anumber of cycles. It has further been suggested to utilize a belt formof brush which passes over mandrels having an electrical field appliedthereto which tends to attract toner from the plate as the brush engagesthe plate and to repel toner from the brush as While the brush and webcleaning apparatus of the prior devices satisfactorily clean theelectrostatic plate for a limited number of operations, they aregenerally complex and occupy a great deal of space in the electrostaticprinting apparatus, thereby preventing such machines from being compact.Both the brush-type cleaner and the web-type cleaner must be frequentlyreplaced due to wear and accumulation of toner particles on theindividual brush and web fibers. In addition, an elaborate and noisyvacuum and filtering system is necessary to collect the residual tonerparticles removed from the electrostatic plate.

A further prior art approach has suggested the utilization of a cleaningroller made of a resilient or elastic material such as natural orsynthetic rubber or sponge which is mechanically biased in compressedrolling contact against the electrostatic plate. The rubber roller iscontinuously cleaned by a brush which dislodges toner particlestherefrom at a postion that is not adjacent the plate. While such aroller provides excellent cleaning characteristics over a relatively fewnumber of reproduction cycles while operating at relatively lowprocessing speeds, it soon becomes clogged with toner particles and isno longer effective in removing toner from the plate. Further, thedevice relies upon the mechanical scrubbing action to effect thecleaning operation. This action is often not great enough to dislodgehighly charged toner particles from the electrostatic plate and to carrythe toner particles away therefrom to a point whereat the tonerparticles may be readily removed from the roller.

SUMMARY In order to overcome the above-noted shortcomings of the priorart and to provide a compact cleaning apparatus which consistentlycleans large quantities of residual toner from an electrostatic plateover numerous reproduction cycles without becoming appreciably worn orclogged with toner, a continuous wiper cleaning member having an outerlayer of compliant material which has a resistivity of less than l0 ohmcentimeters and an outer skin thereon is utilized to wipingly engage theelectrostatic plate in compressed rolling contact therewith to removetoner therefrom. The conductive material is connected to a currentsource such as ground, thereby allowing an image charge to be producedon the outer skin surface of the wiper member which is opposite in signbut equal in magnitude to the charge on the toner particles in proximitytherewith. Since the image charge is produced regardless of the sign ofthe toner charge, toner particles of either polarity of charge may besimultaneously cleaned from the plate. The image charge causes the tonerparticles to adhere to the wiper surface as it moves away from theelectrostatic plate. The toner particles may thereafter be readilycleaned from the outer skin surface of the wiper member since the tonerparticles are not deeply entrained therein. Therefore, the wiper memberremains relatively free of trapped toner particles and can be readilyreused over numerous cycles of operation. The low resistivity of theouter skin enables high processing speeds since the requisite imagecharge is rapidly produced.

A further benefit that is obtained by utilizing a conductive cleaningroller is that the photoconductive surface is completely dischargedthereby. Such uniform 3 discharge of the photoconductor eliminates theneed for a post clean erase lamp in the system.

Accordingly, it is the principle object of the invention to provide andimproved reusable electrostatic plate cleaning system.

It is a further object of this invention to provide a compact cleaningsystem for use in an electrostatic reproduction machine.

A still further object of this invention is to provide a cleaning memberfor cleaning toner from an electrostatic plate which itself can bereadily purged of toner thereon.

The foregoing objects, features, and advantages of the invention will beapparent from the following more particular description of the preferredembodiments of the invention as illustrated in the accompanying drawmg.

IN THE DRAWING FIG. 1 is a schematic illustration of a conventionalelectrostatic reproduction apparatus incorporating the cleaningapparatus of the present invention.

FIG. 2 is a three-dimensional schematic illustration of the wiper memberof the cleaning apparatus of the present invention.

FIG. 3 is a schematic illustration depicting the physical parameters ofthe cleaning apparatus of the present invention.

FIG. 4 is a schematic illustration of an alternate wiper member for usewith the cleaning apparatus of the present invention.

DESCRIPTION Referring now to the drawings, and more particularly to FIG.1 thereof, a schematic illustration of a conventional electrostaticreproduction apparatus incorporating the cleaning apparatus of thepresent invention is depicted.

The reproduction apparatus comprises a plurality of processing stationslocated about a cylindrically shaped electrostatic photosensitive plate11. The cylindrical plate comprises a layer of photoconductive materialsuperimposed over a conductive non-magnetic backing layer. A suitablephotoconductive material is disclosed in U.S. Pat No. 3,484,237, issuedDec. 16, 1969. The backing layer can comprise a substrate made of aninsulating material sprayed with aluminum, the aluminum providing arequisite conduction path to ground.

The photoconductive material is sensitized by a charge corona 13 as theplate rotates therepast in the direction of arrow 15. A light image ofthe copy 17 to be reproduced is projected onto the sensitized surface ofthe electrostatic photosensitive plate 11 rotating thereunder to form anelectrostatic latent image thereon. The rotating plate thereafter passesa magnetic brush developing station 19 whereat multiple componentdeveloper material including electrostatically charged toner is appliedto the surface of the electrostatic photosensitive plate 11 containingthe electrostatic latent image thereon. The charged toner particles arepreferentially attracted to the latent image on the the surface of theplate and then past a pre-clean lamp 26 which discharges thephotoconducitve surface.

. Thereafter, the plate rotates past the cleaning station plate 11 andare subsequently transferred to a support The plate 11 continues torotate past a pre-clean co- 7 rona 25 which charges the residual'tonerparticles on 27 which removes the residual toner from the surface of theplate prior to the arrival of the plate at the charge corona 13.

When utilizing the photoconductive material described in theaforereferenced U.S. Pat. No. 3,484,237, and when producing positiveimages thereon, the

charge corona 13 applies a uniform negative charge to i the plate 11.When thusly making a positive image, light emanating from the ligherareas of the copy 17 discharges the photoconductor so that a negativecharge pattern corresponding to the dark areas on the copy 17 remains onthe plate 11 as it rotates toward the magnetic brush developing station19.

The detailed operation of the magnetic brush developing station isdescribed in the aforereferenced copending application of Allison H.Caudill, et al. The magnetic brush developing station 19 is continuouslyoperable and contains a multi-component developer material which isapplied to the plate 11 as it rotates therepast. The principlecomponents of the developer material are electroscopic toner andaferromagnetic carrier material. Suitable materials for use as tonersare well known in the art and generally comprise finely divided resinousmaterials capable of being attracted and held by electrical charges.Examples of toners which can be employed are commercially marketed bythe International Business Machines Corporation as IBM part no. 1162057and IBM part no. 1162051. The IBM part no. 1162057 toner comprises acopolymer of styrene/n-butylmethacrylate resin, maleic anahydridemodified polyester, polyvinyl stearate plasticizer, and carbon blackpigment. The IBM part no. 1 162051 toner comprises a copolymer ofnbutymethacrylate/methymethacrylate resin, maleic anahydride modifiedpolyester, polyvinyl butyral plasticizer, carbon black pigment, and afumed silica physically mixed in the toner after compounding.

Many well-known suitable ferromagnetic carrier materials can beutilized, the carrier particles generally being between 50 and 1,000microns in size. Often, the carrier particles are manufactured bycoating a ferromagnetic core or bead with a material whichtriboelectrically interacts with the selected toner to produce a desiredcharge on the toner in order to provide good imaging quality. An exampleof such a carrier and the method by which it can be made to obtain adesired triboelectric characteristic for any selected toner is dis- 7closed in the aforereferenced copending application of William J. Kukla,et al.

As has been described, the toned image leaving the magnetic brushdeveloping station 19 is transferred to a support surface 21. Thetransfer corona creates an electrostatic charge on the support surfacecausing the toner to be preferentially attracted thereto from thesurface of the electrostatic photosensitive plate v11. Since the toneris triboelectrically charged positive, the

transfer corona 23 applies a negative charge to the support surface 21causing the toner to be attracted thereto.

While the major portion of the toned image is transferred to the supportsurface 21, a residual toned image remains which must be cleaned fromthe electrostatic photosensitive plate 11 prior to a subsequent imagingcycle. Accordingly, the residual toner image is rotated past a pre-cleancorona 25 which places a charge on the toner to facilitate electrostaticremoval of the toner from the plate 11. As will be describedhereinafter, the cleaning apparatus removes toner which has been chargedto either sign (e.g., positively and negatively charged toner).Accordingly, the pre-clean corona 25 can be an AC corona therebycharging the toner to both polarities, a positive corona which tends toenhance the positive triboelectric charge on the toner or a negativecorona which, in conjunction with the transfer corona 23, tends to causethe majority of the toner particles to be charged negatively. It hasbeen found that the most satisfactory results occur with a negativepre-clean corona. The pre-clean lamp 26 illuminates the plate 11 therebydischarging electrostatic charges existing on the plate 11 which mightotherwise tend to attract toner thereto.

The residual toned image thereafter passes cleaning station 27. Thecleaning station 27 comprises a wiper roller 31 for removing tonerparticles from the plate 11. The wiper roller 31 is mounted for rotationin the direction of arrow 33 at a surface velocity between 6 and inchesper second when the plate 1 1 rotates at a surface speed of 9.3 inches asecond. The wiper roller 31 is approximately 3 inches in diameter and isbiased into the plate 11 for wiping engagement therewith.

The wiper roller 31 is shown in detail in FIG. 2 and comprises an outerlayer 35 of a conductive compliant elastomer material. An example of asuitable elastomer material is a silicone rubber produced by the AmesRubber Company having formulation number ARX5424 which is a siliconerubber having conductive carbon particles embedded therein, the carbonparticles comprising 26 to 41 percent by weight of the material. Otherelastomer materials such as conductive neophrene, conductive urathane,or conductive ethylene propylene terpolymer have also been successivelyutilized. The outer skin of the conductive silicone rubber material hasa compliance as measured on a Shore A2 scale of 60 or softer, aresistivity of 10* ohm.- centimeters and a surface smoothness having anaverage height asperity of 200 micro inches.

The wiper roller 31 further comprises a conductive metallic core 37 madeof materials such as aluminum or hardened steel. A non-conductiveplastic roller could also be utilized. A compliant material layer 39comprising a foam material such as conductive neophrene or urathane foamis mounted on the core 37 and provides additional cushioning tocompensate for mechanical tolerance variations between the wiper roller31 and the plate 11 and insures an adequate sized cleaning footprint 40.

Referring again to FIG. 1 of the drawings, the wiper roller 31 isengaged by a scavenge roller 41 which removes toner particles from thewiper roller 31. The scavenge roller 41 is in turn scraped by a knifeblade 43 which removes the toner particles to the lower portion of thecleaning station 27 whereat they are removed by the continuouslyrotating auger 45. The scavenge roller 41 may be a conductive smoothroller as depicted in FIG. 1 or a roller which is made of an insulatormaterial such as nylon which triboelectrically interacts with the tonerparticles on the wiper roller 31 to effect removal there-0f. Asdepicted, the scavenge roller 41 is a conductive steel roller which isgrounded at current source 47. The current source 47 is therebyconnected through the scavenge roller 41 to the outer skin of the wiperroller 31.

Referring now to FIG. 3 of the drawings, a schematic illustrationdepicting the physical parameters of the cleaning apparatus of thepresent invention is depicted. As previously indicated, toner particles51, 52 having a charge of either polarity are located on the surface ofthe plate 11 as it rotates in the direction of arrow 15 toward the wiperroller 31. The toner particles are retained on the surface of the plate11 by adhesion forces and, to a lesser extent, by electrostatic forces.The adhesion forces are greater than the electrostatic forces sincethese forces prevented the toner from transferring at the transferstation.

As the toner particles 51, 52 are wipingly engaged by the wiper roller31, the adhesion forces causing the toner particles to remain on theplate 11 are mechanically overcome thereby causing the toner particlesto become dislodged from the plate 11. As the thusly dislodged chargedtoner particles come in proximity to the conductive outer skin of theouter layer 35, an image charge is produced at the surface of the outerlayer 35 equal in magnitude but opposite in sign to the charge on thetoner particles. The image charge is produced by the current which flowsfrom the current source 47 through the scavenge roller 41 and throughthe conductive outer layer 35 to that area of the surface adjacent thecharged toner particle.

Since it is easier for the dislodged toner particles to progress out ofthe nip formed by the rollers 31 and 41 rather than further into thenip, the toner particles tend to move with wiper roller 31 in thedirection of arrow 33. Further, since the adhesion forces aremechanically broken, the image charge on the outer surface of the wiperroller 31 acts on the toner particles thereby causing the tonerparticles to adhere to the outer skin of the outer layer.35 as itrotates away from contact with the plate 1 1.

Continued rotation of the wiper roller 31 in the direction of arrow 33brings the wiper roller into contact with scavenge roller 41 rotating inthe direction of arrow 61. The toner particles 57, 58 are held to thesurface of the wiper roller 31 by an image charge as has been explainedheretofore. As these particles enter the nip between rollers 41 and 31,they are again mechanically dislodged. Since it is easier for the tonerparticles to progress out of the nip than further into the nip, theytend to remain on the scavenge roller 41. An image charge is produced onthe surface of the scavenge roller in a manner analogous to theproduction of the image charge on the wiper roller 31 as previouslydescribed which causes the toner particles to remain on the surfacethereof until they are mechanically dislodged by the knife blade 43 asthe scavenge roller 41 rotates therepast in the direction of arrow 61.

It should be noted that the coefficient of friction of the outersurfaces of the plate 11, the wiper roller 31, and the scavenge roller41 are chosen so that there is a greater coefficient of friction betweenthe toner particles and the wiper roller 31 than between the tonerparticles and the surface of the plate 11. Further, there is a greatercoefficient of friction between the surface of may be sized bycontrolling the smoothness of the respective rollers.

As has been described heretofore, a non-conductive scavenge roller 41can be' utilized in lieu of a conductive roller, the requisite currentsource connection to the wiper roller 31 being made directly from thecurrent source 47 to the roller 31. When insulator materials such asnylon are utilized for the scavenge roller 41, the nylon materialtriboelectrically charges the toner particles located on the surface ofthe wiper roll 31 as these toner particles progress into the nip betweenthe rolls 41 and 31. The triboelectric charge created at the surface ofnylon roll provides a slightly stronger force than the image chargediscussed with respect to a conductive roll thereby facilitating removalof the toner particles from the wiper roll 31.

Referring now to FIG. 4 of the drawings,-a schematic illustration of analternate wiper member for use with the cleaning apparatus of thepresentinvention is depicted. In this embodiment, the cleaning station 27comprises two mandrels, 71, 73, over which a belt 75 of wiper materialis mounted. The belt 75 can comprise a single layer ofconductive'elastomer material such as silicone rubber. The'be'lt 75 ismounted for movement in the direction of arrow 77 and wipirigly engagestoner particles located on the surface of the plate 11 as it moves intocontact therewith. The wiping engagement of the compliant layermechanically dislodges the toner particles. The mandrel 71 is connectedto ground thereby providing a current to the outer skin of the belt 75to create an image charge equal to but opposite in sign from the chargeof the toner particles in proximity thereto. The image charge causes thetoner particles to be retained on the outer skin of the belt 75 as itrotates away from the plate 11 toward the knife blade 43. The knifeblade 43 wipes directly against the belt 75 scraping toner therefrominto the continuously moving auger 45.

Referring once again to FIG. 1 of the drawings, it has been found thatbest of cleaning results are obtained when the outer skin of the wiperroller 31 is relatively smooth. Thus, a surface having an averagesurface height asparity in a range between and 400 micro inches,depending upon the material selected, provides the best cleaningresults. However, a porous or irregular outer skin also producessatisfactory cleaning re-' sults although care must be taken to select aproper mechanism such as a biased rotary brush to dislodge toner whichmay accumulate in the pores of such a wiper member.

. As noted heretofore, the resistivity of the outer layer 35 of thewiper roller 31 that is required to achieve satisfactory cleaningresults is dependant upon the processing speed of the apparatus. This isbecause the re sistivity of the outer layer must be sufficiently low toenable a current to flow rapidly therethrough to create the requisiteimage charge on that portion of the surface thereof in proximity with acharged toner particle before that portion of the surface rotates awayfrom the plate 11. An increase in processing speed produces acorresponding decrease in the time that a given portion of the outerlayer 35 contacts the plate 11. Thus, increased processing speedsrequire a corresponding decrease in resistivity.

Other factors which determine the requisite resistivity of the outerlayer 35 include the thickness of the outer layer, the length of thefootprint 40 (contact distance)'and the capacity of the toner particles.When utilizing the afore referenced IBM part number toners,

the radius of an average toner particle is 5 microns, and

its relative dielectric constant is 6,6,, E (3)(8.85 X 10 Thus itscapacity is r/e e,,= 1.8 X 10 The requisite resistivity of the outerlayer 35 may therefore be calculated by the following equation:

where l is the length of the footprint V is the relative velocity of theplate 11 and roller t is the thickness of the outer layer 35 (cm) p isthe resistivity of the outer layer (ohm cm) When utilizing minimummaterial thicknesses (e.g., 10 mils) it has been found that forprocessing speeds ranging from 3 to 20 inches per second, elastomermaterials having a resistivity greater than 10 ohm centimeters fail toadequately-remove charged toner from the plate 11 since the timeconstant of such materials I is too great to enable an image charge tobe produced rapidly enough to be effective. It is to be noted thatslower systems employing extremely thin outer layers and largefootprints could utilize materials having resistivities in the range of10 to 10 ohm centimeters. However, compliant materials in this range ofresistivity exhibit large scale resistivity variations with temperaturethereby causing the cleaning system to be marginal. Further, minutechanges in doping levels of such materials effect large resistivitychanges thereby greatly adding to the manufacturing costs thereof.

It is further noted that while elastomer materials having lowerresistivity than 10 ohm centimeters adequately supply an image charge,care must be taken in controlling the amount of conductive particlesembedded in the elastomer since the amount of conductive particlescontrols the compliance of the material as well as its resistivity.

The importance of controlling the resistivity and surface smoothness ofthe outer layer 35 of the wiper roller 31 of FIG. 1 is demonstrated bythe following example.

A robot having a cleaning station like that depicted in FIG. 1 andhaving a processing speed of 20 inches per second and a wiper rollersurface velocity of 6 to 8 inches per second and a footprint 40 about0.125 inches long'was constructed. The outer layer 35 of the wiperroller 31 consisted of a porous neophrene layer of materialapproximately 0.062 inches thick having a resistivity of 10 to 10 ohm.centimeters. Failure of the wiper roller to remove toner from therotating plate 11 without smearing occurred within 1,000 cycles ofoperation. Thereafter, the wiper roller 31 was replaced with a wiperroller 31 having an outer layer 35 consisting of a porous neophrenelayer approximately 0.062

inches thick and having a resistivity of 10 ohm. centimeters. Failureoccurred after approximately 20,000 cycles of operation. The wiperroller 31 was then replaced with a wiper roller 31 having an outer layer35 consisting of a smooth neophrene layer approximately 0.062 inchesthick and having a resistivity of 10 ohm.- centimeters. Failure occurredafter 100,000 cycles of operation.

As noted heretofore, a ground potential current source 47 may beconnected to the wiper roller 31 in order to cleanthe plate 11 of tonerwhich is charged to either polarity. A current source 47 having arelatively low DC. potential (e.g., 10 to 50 volts) may be utilized whenit is desirous to clean toner which is substantially charged to apolarity opposite the polarity of the supply.

An added benefit obtained by utilizing a conductive cleaning member isthe complete discharge of the photoconductive plate 11 effected thereby.Previous cleaning devices which mechanically dislodged toner particlesfrom the plate left the plate with an electrostatic charge thereon atthe location whereat the toner particle was attached thereto. Thischarge often had to be eliminated with a post-clean erase lamp Suchplate charges are eliminated by providing a conductive path to thephotoconductor with the conductive cleaning roller after the tonerparticle has been removed therefrom. Thus continued motion of the plate11 past the cleaning roller causes electrostatic charges on the plate tobecome neutralized.

While the foregoing invention has been particularly shown and describedwith reference to a preferred embodiment thereof, it should beunderstood by those skilled in the art that the foregoing and otherchanges in form and detail may be made therein without departing fromthe spirit and scope of the invention.

What is claimed is:

1. Cleaning apparatus for removing electrostatically charged tonerparticles from the surface of an electrostatic plate comprising: 7

a continuous wiper means mounted for movement in a closed loop in wipingengagement with the surface of the electrostatic plate containing tonerparticles attracted thereto for removing said toner particles from saidelectrostatic plate, said wiper means comprising at least an outer layerof a compliant material having a resistivity of less than l0 ohm.centimeters and having an outer skin thereon;

cleaning means engagingly connected to said wiper means for removingtoner therefrom;

drive means for moving said wiper in said closed loop past saidelectrostatic plate and past said cleaning means;

a current source connected to said wiper means for supplying current tothe outer skin of said, wiper means proportional to the image charge ofthe toner in contact therewith.

2. The cleaning apparatus set forth in claim 1 wherein said outer skinhas a smooth outer surface thereon.

3. The cleaning apparatus set forth in claim 1 wherein saidelectrostatic plate is mounted for motion in a first direction and saidwiper means engages said plate when moving in a direction opposite saidfirst direction.

4. The cleaning apparatus set forth in claim 1 wherein said currentsource comprises a grounded connection.

5. The cleaning apparatus set forth in claim 4 further comprising apreclean corona unit for electrostatically charging said toner on saidplate prior to said toner being engaged by said wiper means toward apolarity opposite its polarity established when applied to the plate.

1. Cleaning apparatus for removing electrostatically charged tonerparticles from the surface of an electrostatic plate comprising: acontinuous wiper means mounted for movement in a closed loop in wipingengagement with the surface of the electrostatic plate containing tonerparticles attracted thereto for removing said toner particles from saidelectrostatic plate, said wiper means comprising at least an outer layerof a compliant material having a resistivity of less than 10 8 ohm.centimeters and having an outer skin thereon; cleaning means engaginglyconnected to said wiper means for removing toner therefrom; drive meansfor moving said wiper in said closed loop past said electrostatic plateand past said cleaning means; a current source connected to said wipermeans for supplying current to the outer skin of said wiper meansproportional to the image charge of the toner in contact therewith. 2.The cleaning apparatus set forth in claim 1 wherein said outer skin hasa smooth outer surface thereon.
 3. The cleaning apparatus set forth inclaim 1 wherein said electrostatic plate is mounted for motion in afirst direction and said wiper means engages said plate when moving in adirection opposite said first direction.
 4. The cleaning apparatus setforth in claim 1 wherein said current source comprises a groundedconnection.
 5. The cleaning apparatus set forth in claim 4 furthercomprising a preclean corona unit for electrostatically charging saidtoner on said plate prior to said toner being engaged by said wipermeans toward a polarity opposite its polarity established when appliedto the plate.